/*
 * Copyright (C) 2006 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.util.concurrent.AbstractFuture.TrustedFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.annotation.Nullable;

/**
 * Implementations of {@code Futures.immediate*}.
 */
@GwtCompatible(emulated = true)
abstract class ImmediateFuture<V> implements ListenableFuture<V> {
    private static final Logger log = Logger.getLogger(ImmediateFuture.class.getName());

    @Override
    public void addListener(Runnable listener, Executor executor) {
        checkNotNull(listener, "Runnable was null.");
        checkNotNull(executor, "Executor was null.");
        try {
            executor.execute(listener);
        } catch (RuntimeException e) {
            // ListenableFuture's contract is that it will not throw unchecked exceptions, so log
            // the bad
            // runnable and/or executor and swallow it.
            log.log(Level.SEVERE,
                    "RuntimeException while executing runnable " + listener + " with executor " + executor, e);
        }
    }

    @Override
    public boolean cancel(boolean mayInterruptIfRunning) {
        return false;
    }

    @Override
    public abstract V get() throws ExecutionException;

    @Override
    public V get(long timeout, TimeUnit unit) throws ExecutionException {
        checkNotNull(unit);
        return get();
    }

    @Override
    public boolean isCancelled() {
        return false;
    }

    @Override
    public boolean isDone() {
        return true;
    }

    static class ImmediateSuccessfulFuture<V> extends ImmediateFuture<V> {
        static final ImmediateSuccessfulFuture<Object> NULL = new ImmediateSuccessfulFuture<Object>(null);
        @Nullable
        private final V value;

        ImmediateSuccessfulFuture(@Nullable V value) {
            this.value = value;
        }

        // TODO(lukes): Consider throwing InterruptedException when appropriate.
        @Override
        public V get() {
            return value;
        }
    }

    @GwtIncompatible // TODO
    static class ImmediateSuccessfulCheckedFuture<V, X extends Exception> extends ImmediateFuture<V>
            implements CheckedFuture<V, X> {
        @Nullable
        private final V value;

        ImmediateSuccessfulCheckedFuture(@Nullable V value) {
            this.value = value;
        }

        @Override
        public V get() {
            return value;
        }

        @Override
        public V checkedGet() {
            return value;
        }

        @Override
        public V checkedGet(long timeout, TimeUnit unit) {
            checkNotNull(unit);
            return value;
        }
    }

    static final class ImmediateFailedFuture<V> extends TrustedFuture<V> {
        ImmediateFailedFuture(Throwable thrown) {
            setException(thrown);
        }
    }

    static final class ImmediateCancelledFuture<V> extends TrustedFuture<V> {
        ImmediateCancelledFuture() {
            cancel(false);
        }
    }

    @GwtIncompatible // TODO
    static class ImmediateFailedCheckedFuture<V, X extends Exception> extends ImmediateFuture<V>
            implements CheckedFuture<V, X> {
        private final X thrown;

        ImmediateFailedCheckedFuture(X thrown) {
            this.thrown = thrown;
        }

        @Override
        public V get() throws ExecutionException {
            throw new ExecutionException(thrown);
        }

        @Override
        public V checkedGet() throws X {
            throw thrown;
        }

        @Override
        public V checkedGet(long timeout, TimeUnit unit) throws X {
            checkNotNull(unit);
            throw thrown;
        }
    }
}
